Method of grounding shielding tape at terminal of insulated conductors



NVENTOR ATTO RNEIYS LATED CONDUCTORS pT 79 lgn GRE METHOD oT GROUNDING SHTELDTNG TAPE AT TERMINAL oT INSU Filed Dec, 25, 1934 @N mw w Patente-d Apr. 7, 1936 Until@ Para GFFIQE METHOD F GROUNDING SHIELDING TAPE AT TERMINAL OF TORS INSULATED CONDUC- Bjorn Jore, Hastings upon Hudson, N. Y., as-

signor to Anaconda Wire & Cable Company,

s 'l' Claims.

My invention relates to terminals for insulated electric cables or conductors that are shielded with a metallic envelop which in turn is protected from the air and the elements, and it relates more particularly to means and mehods for grounding such metallic shields.

Heretofore shields of the above type have been grounded by removing the protective covering about theshield at a distance from its connection to a terminal connector and then clamping onto the metallic surface of the shield thus exposed a clamp which is in turn connected to ground. The removal of the protective covering, usually an impregnated vbraided material, exposed the metallic sheath to the atmosphere and permitted moisture to enter beneath the outer protective covering and penetrate between the insulation and the shielding tape. This exposed the insulation to deterioration and sometimes to ultimate dielectric breakdown.

In my present invention these defects are obviated and a grounding'means and method are provided'in which the metallic shield and the insulation between the shield and the conductor are covered and protected against the entrance of moisture or air or other disintegrating or destructive agents.

The various features of my invention are illustrated in the accompanying drawing in which Fig. 1 shows a conductor and shield terminal embodying a, preferred form of the invention; Figs. 2 and 3 are views showing the shield in successive stages of construction; and Fig. 4 is a 1ongitudinal section, on a larger scale, of the cable and grounding shield and connections.

In the accompanying drawing the invention is illustrated as applied 'to a cable having a central core I0 and an enclosing sheath II of rubber or other suitable insulating composition. -The end of the conductor I0 is received in and secured to a terminal lug I2. The insulation I I is continued to approximately the lug I2, a wrapping I3 of tape being provided between the lu'g I2 and the insulation II. It will be understood that this cable construction is shown merely for purposes of illustration and that other arrangements of con ductor and insulation may be used.

The cable also has a metallic sheath I4 wrapped or laid or braided about the insulation II. rhe shield I4 is in turn covered by a layer I5 of protective material to prevent injury to the shield insulation and to prevent the access to the latter of moisture or corrosive agents. grounding terminal for the shield I4 the latter is r cut back to a suicient distance from the lug I2 In forming a and terminates as indicated at I6 in 4. The protective covering I5 is cut back somewhat further so as to expose the shield for a short distance, as for example one-half inch. A wrapping I'I of insulating tape is then formed on the insulating jacket III beginning at the point I6 and continuing for a short distance on the insulation. This wrapping il gradually increases in diameter from the point i5 where its diameter approaches that of the jacket Il to a maximum and then decreases. The shield i4 is then provided with an extension of gradually increasing diameter by wrapping the exposed end of the sheath between the point I6 and the end ofthe covering I5 with a suitable metallic element, as for example a metal braid or mesh I. This may be done by wrapping one end of the braid I8 about the exposed surface .of the shield and then in helical fashion onto the expanding surface of the tape winding I1. lt will be apparent that with this construction the metallic enclosing sheath element is expanded so that its edge has a diameter considerably greater than that of a shield I4 and is separated from the conductor I0 by an added quantity of insulation thereby preventing a concentration of stress on the insulation II at the termination of the extended shield I8.

A band or braid I9 of conducting metal, such as copper, is then laid longitudinally along the conical structure I8 overlapping the surface of the shield I4 and is secured to the conical mesh structure I8 and to the exposed end of the shield thus forming a unitary structure and a good electrical connection between the three elements. This may be accomplished by soldering.

Several layers of rubber tape are then wrapped over the cone and ground lead from the end of the protective coating I5 to approximately the termination of the metal cone. The band or braid I9 is then bent back over the rubber tape and for a short distance onto the covering I5 and is then secured to a terminal connector 20. Thebraid I9 is then lled and saturated with a rubber cementing compound so that the interstices are completely lled and the surface completely coated. Several layers 2| of rubber tape are then applied by wrapping them around the structure so as to cover the braided lead or band I9 throughout its entire exposed length from the clamp 20. A seal against the' entrance of moisture is formed between the braided copper lead I9, the rubber tape and the structure I8. Layers 22 of friction tape are then wrapped over the rubber tape and the entire structure is painted with a water-proof paint to make a double seal against the entrance of moisture or destructive reagents. Through the above construction, therefore, the part of the shield and terminal parts of the insulating material at which the connection is made to a ground clamp are thoroughly covered and sealed against the entrance of moisture or destructive agents While at the same time a very effective electrical connection is made from the shield to ground.

What I claim is:

l. A cable terminal comprising a conductor, insulation enclosing said conductor, a metallic shield encircling said insulation and terminating short of the end o f said insulation, a protective covering of insulating material for said shield terminating short of the end of said shield and a flaring metallic extension on said shield beyond the end of said protective covering, a lead wire extending from said flaring extension to a ground clamp and a protective covering of Water resistant material enclosing said lead and said flaring extension and sealing the latter from the entrance of moisture.

2. A cable terminal comprising a conductor, an insulation for said conductor, a metallic shield enclosing said insulation and terminating short of the end thereof, a protective covering of insulating material for said shield, .said insulation being increased in diameter for a short distance beyond the end of said shield, a metallic wrapping extending from the end of said shield onto said enlarged insulation, a protective covering of Water resistant insulating material for said WrappingA and a lead extending through said covering, and means for sealing said lead to prevent entrance of moisture to said metallic Wrappings.

3. A cable terminal comprising a conductor, an insulation. for said conductor, a protective metallic shield about said insulation and terminating short of the end of said conductor, a protective covering of Water resistant insulating material for said shield, said insulation being increased in diameter beyond the end of said metallic shield and a metallic extension from said shield onto the enlarged insulation, a protective covering of Water resistant insulating material for said extension, a braided wire lead from said extension through said protective covering of said extension, said lead being impregnated and filled with moisture-proofing material to seal said extension from moisture.

1 -A cable terminal comprising a conductor, an insulation for said conductor, a protective metallic shield about said insulation and terminating short of the end of said conductor, a water resistant insulating protective covering for said shield, said insulation being increased in diameter beyond the end of said metallic shield and a metallic extension from said shield onto the enlarged insulation, a Water resistant insulating protective covering for said extension, a braided Wire lead from said extension through said protective covering, said lead being impregnated and lilled with moisture-proong material to seal said extension from moisture, said lead and extension and shield being secured together by solder.

5. The construction of claim 3 in which said lead extends backwardly over said protective covering and a clamp secured to said lead and secured on said cable.

6. The construction of claim 3 in which said lead extends backvvardly over said protective covering and a clamp secured to said lead and secured on said cable, said returning lead being embedded in protective material to prevent entrance of moisture.

7. A cable terminal construction which comprises a conductor, a securing terminal for said conductor, insulation enclosing said conductor and the joining end of said terminal, a metallic protective sheath on said insulation terminating at a distance from said securing terminal, a water resistant insulating covering to protect said metallic shield from the atmosphere, said insulation flaring outwardly to an increased diameter heyond the end of said protective sheath, a metallic extension from said sheath onto said flaring insulation, a clamp on said cable short of the end of said metallic sheath and a connection from said shield extension to said clamp and a Water resistant insulating protective material enclosing said extension and said connection and sealing said extension from moisture.

BJORN JORE. 

